Combination clutch



WQ P. LEAR Sept. 10, 1963 3,103,604 COMBI-NATION CLUTCH, FLYWHEEL, AND ELECTRIC GENERATOR ROTOR;k

5 Sheets-Sheet 1 original Filed May 1, 1958 INVENTOR W/LL/M R .EP

ATTORNEY sept.,1o, 1963 COMBINATION CLUTCH, RLYWHEEL, AND ELECTRIC GENERATOR RoToR I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I z I INVENTOR W/LL/A M H EAR BY Q ATTORNEY w. P. LEAR 3,103,694,-

Sept. 10, 1963 w. P. LEAR 3,103,604

COMBINATION CLUTCH, FLYWHEEL, AND ELECTRIC GENERATOR ROTORk original Filed May 1, 195s 5 sheets-sheet s INVENTOR W/LL IAM R 'LE/1P BY /Z- @5% ATTORNEY W. P. LEAR COMBINATION CLUTCH, FLYWHEEL, AND ELECTRIC GENERATOR ROTOR Sept. 1Q, 1'963 5 Sheets-Sheet 4 a 8 4 8 g A m Original Filed May 1, 1958 INVENTOR W/LL/AM R LEA/5? ATTORNEY w. P. LEAR 3,103,604

COMBINATION CLUTCH, FLywHEEL, AND ELECTRIC GENERATOR RoToR sept. 1o, 1963 5 Sheets-Sheet 5 Original Filed May 1, 1958 THPOTTLL'" INVENTOR' M, p m 2..

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ATTORNEY United States Patent O l" COMBINATION CLUTCH, FLYWHEEL, AND ELECTRIC GENERATOR ROTOR William P. Lear, Pacific Palisades, Calif., assignor to Lear Siegler Inc., Santa Monica, Calif., a corporation of Delaware Original application May 1, 1958A, Ser. No. 732,393, now PatentA No. 2,981,069, dated Apr. 25, 1961. Divided and this application July 6,1960, Ser. No. 46,859

6 Claims. (Cl. 3104-78) This invention relates to thepropulsion of aircraft and, in particular, to a system for driving an aircraft propeller by means of two independent aircraft engines, either of which may be de-coupled from the propeller upon malfunctioning.

This patent application is a divisional application restricted to the non-elected claims of co-pending patent application Serial No. 732,393, filed May l, 1958, noW Patent No. 2,981,069, inthe name of William P. Lear, for Twin-Engine Aircraft Propeller Drive.

Propeller driven aircraft are logically divided into two major classes: the single engine class andmulti-engine class. A single engine airplane has the pre-eminent advantage of minimum drag-per-horsepower of the engine, and the disadvantage of total dependence upon a single power plant.: The multi-engine aircraft, on the other hand, suffers from increased aerodynamic drag due to the necessity for a number of nacelles, or engine enclosures, equal to the number of engines and totaling a frontal area in excess of the total which `would be required for a single engine having the same horsepower as the total horsepower of the number of engines in the multi-engine aircraft. On the other hand, as is well known, most multi-engine aircraft are capable of functioning, at least in an emergency, on less than the total number of engines. From a dependability standpoint, therefore, the multi-engine aircraft is much to be preferred.

It has long been recognized if one could achieve multi-engine dependability, but with a configuration presenting only a single nacelle to aerodynamic ow, the advantages of the dependability of multi-engine aircraft could be achieved together with the advantage of minimum drag, which is characteristic of the single-engine airplane. IAttempts have therefore been made in the past to place two aircraft engines in the fuselage of an airplane and couple them to a single airplane propeller with a gear box and overrunning clutches. The theory of operation of this arrangement -was that if one of the engines failed to deliver as much torque as the other, its overrunning clutch would be disengaged and the propeller would be driven by the engine whose capabilities had not been impaired. This arrangement, however, has been found to be unsatisfactory for the reason that it is virtually impossible to cause any two aircraft engines to deliver the same torque for any substantial period of time, except under highly idealized test-stand conditions. Variations in intake' manifold pressure due to aerodynamic ow around the airplane,l including gusts, and mechanical difficulties in throttle settings have prevented the practical realization of a theoretically satisfactory idea. fIn actual practice, it has been found that theV overrunning clutches are almost constantly engaging and disengaging because of hunting in the torque output of the two engines. This chattering or alternate engaging and disengaging of the overrunning clutches has led to their early destruction and also the setting up of undesirable torsional oscillations which produced fatigue in the engine and airframe. Also, since the aircraft engines must be fabricated to be of as alight a weight as possible, they rarely, if ever, have been made with a iiywheel to smooth their torque output. The natural pulsations of their 3,103,604 Patented Sept. 10, 1963 ICC aircraft engines to the same propeller has existed.

This invention contemplates apparatus for successfully coupling two independent aircraft engines together, which takes into account the natural roughness in the torque delivery of the conventional aircraft engine. -It further contemplates means for automatically disconnecting either engine from the load when it ceases to deliver torque at the throttle setting commanded and commences to be a drag on the other engine. It further contemplates the provision of a novel means of eliminating torsional harmonic oscillations ordinarily associated with aircraft engines` powering a multi-element drive mechanism.

This invention has for its primary object the provision of an aircraft propeller driven system having multi-engine dependability and single-engine simplicity and aerodynamic eiciency.

It is another object of this invention to provide a mechanical clutching system for connecting either or both of two engines to a single driven member, which system is responsive to failure of either engine in operation.

It is another object of this invention to provide a novel means for disconnecting an aircraft engine from its load when the engine malfunctions.

-It is another object of this invention to provide a twoengine aircraft propeller drive system which is operative to disconnect one engine when it malfunctions, but which remainsy connected irrespective of malfunction When less than a predetermined throttle setting is effected.

Other objects of the invention will become apparent from the following description taken in connection with the accompanying drawings, in which: l

F-IG. l is a block diagram of the invention;

iFIG. 2 is a side view of the nose portion of an airplane including this invention;

FIG. 3 is an over-all schematic of the invention;

FIG. 4 is an end view of the device shown in FIG. 3;

FlG. 5 is a detailed elevational view, partly in section, of the clutch and alternator portion of this invention;

FIG. 6 is a circuit diagram of a portion of the invention; and v FIG. 7'is an end view of the `device shown in FIG. 5. Referring now to the drawings and, in particular, to FIGS. l and 2, enginesl and 2 are operative to drive propeller-3 under normal conditions. Engine 1 is physically coupled to flywheel 4 which, in turn, is connected by clutch 5 to gear box `6 which, in turn, drives propeller 3. Engine y2 is connected to drive iiywheel 7 which, in turn, drives clutch 8 which, through gear box 6, also drives propeller 3. Engines 1 and 2 are both mounted on airframe 9 by conventional shockmounting, but interposed between the engine and airframe in any suitable manner, including a manner to be shown hereinafter by way of example, are torque sensors 10 and 11 whose function it is to sense the magnitude and direction of torque reaction between the airframe and each engine. Torque sensors 10 and 11 have an output which is fed to time delay devices 12 and 13, respectively, as shown in FIG. l, and thereafter to disconnect switch 14. Disconnect switoh 14 serves to operate clutch actuators 15 andV 16 which, in turn, operate clutches 5 and 8, respectively. `Cl-utoh actuators 15 and 16 also may be operated FIG. 1 isas compact as possible and presents approxi-V mately the same frontal Varea to aerodynamic flow as that of a single engine, with enginel being located below and forward ofenlgine 2 andwit'h the gearbox vand clutches all arranged within the forward endl of the aircraft fuselage. Y' f lSyste'nrwise,the device functions in the'following manner. Under normal operatingconditions engines 1 and 2 drive propeller 3 through clutches 5 and 8 which are i 1 normally engaged. E'lywheels 4 and 7 are provided to smooth out the torque output of the engines. As previously related, it is a normalcharacteristic 'of aircrafttype engines which are designed to be of as lightweight as possible, that the torque output is very rough. y113ecause the crankshaft, and in fact all parts of the engine, are made to be only as heavy as is absolutely, required to withstandthe'loads for which they arerdesigned, there is a1 very` direct relationship ybetween'the power generated in the cylinders and the torque youtput at the shaft. Thus, there y.is verylittle flywheel elect from the rotating parts of an aircraft engine, and in aircraft, flywheels are considered to be an impossible luxury from the weight standpoint.Y yNevertheless, i inl accordance with this invention,I have provided iiywheels 4 and 7 for the purpose of smoothing the torque output of engines 1 and 2.

These ilywheels have been provided for two reasons.

First 'of all, the .provision of these ywheels offers a method 'of virtu-ally .eliminating torsional vibration probinasses which the various shafts and gears connecting the fengines to the propeller represent. Analytically speaking, leach shaftl is a torsionspring and 'each gear',` too,

has its spring characteristics. The' system, looking fromV the engine to the propeller, therefore can-be replaced for analytical Ypurposes by a single spring having a certain predetermined spring constant; The various masses ina single mass, and the system has a certain natural Vtorsional frequency.A A's is well known,'if one .excites a Y lems in "the transmission of power from the'engines to .i

Y the'propeller through Vthelcomplex system of springs `and 1 volved, tooymay be replaced for analytical purposesr by system havingV a certain natural frequency, with a forci ing vibration vor a forcing torsional disturbance approachbration will occur.' The provision of flywheels 4V and'7 eliminates this entire problem rbecause these Yflywheels are made tohave sufficient polar moment yof inertia'to substantially completely smooth thetorque output of the engines.

" ing the natural frequency, destructive amplitudes ol"vi-` With no particular forcing frequency -applied to the mechanical linkage between the flywheel and the propeller, ntorsional vibration is no `longer a problem.

The second reason for using or permitting the use of ywheels 'in this system is thatva novel method has been found for utilizingin a constructuve `manner the massof `excess 'ofV what is normally devoted to the Vpurpose of, Y

electric power `generation in `an aircraft engine.

' In normal operation, therefore,` clutches S and 8 are engaged andrflywlheels 4 and 7 serve the dual purpose of torque smoothing and power generation. VDuring normal cruising conditions, torque sensors 10 andW y11 have no output and clutch actuators 15and 16 -arernot operative 'i to disconnect 'clutchesV 5 and 8. Y ln theV event of failure of, for example, engine'l, torque sensor 10 is operative throughY time delay 12 to throw disconnect rswitch 14.

Clutch actuator 15 is .immediately caused toV "operate f clutch 5 with the result that engine 1 is disconnected from` gearboxf6.V Ihe aircraftthen continues ,to ily, being powered only by engine B. In asimilar manner, failure results in its being disconnected from gear Y of engine 2 box 6. Y g

VIn the event that throttle 19 is reduced .in Ysetting be= low a certain Vpredetermined value, provision is made toy render switch 14 inoperative so that even through ,oneV of the torque sensors senses -a reversal in torque reaction between 'one of the engines and the airframe, that par@V ticular engine will not be disconnected from the load.

It will be apparent that rthis 4feature is necessary for a condition such, for example, Vasa dive, where the airplane propeller is wind-milling and actually driving one or -bothof the engines. .During this condition the throttle is normally retarded to one-third or less of the rate of output ofthe engines and it wouldnot beY desirable ,to

cause -either of the engines to -be disconnected during this condition.

It should "be pointed out that torque sensors l10 Aandwll are sensitive tothe reaction `torque existing between the vengine and the airframe at :all times whenthe engine Vis 1delivering power. Asis well known, if an engine isidesigned for clockwise rotation of its output shaft, acou'nterclockwise torque is applliedfby its mounts to the airframe. New, torque sensors 10 and 11 are normally inoperative when the torque `reaotionis in the sense corresponding to normal outpuh- However, when theengine itself is being ,driven by tli'epropeiler, the natural resistance of the-en-r gine to overspeeding causes a reversalv of torque output to the aircraft, audit is thisreverse torque to which'Y torquesensors 10 and 11 must be sensitive. i

Referring now to FIG. 6, assuming that `the direction of rotation ofthe propeller is counter-.clockwise as viewed from FIG. y6, the reaction torque of engine 1 upon rairrf Y frameY 9 is clockwise, thus, depressingsprings 23 rand-'24 and extending springs 25 :and `26. -Co`mpression of springs -23 ,and 24` causes switches `2.7 and -28 to. remain open so that current from battery 29.-does not reach-winding 30 f of clutch actuator 16 when engine 1=i`s delivering'nonmal torque. e

y, It must be borne in 'mind that clutches 5 and 8 are the flywheel, which would otherwiseV constitute nonaesf Y sential weight for the aircraft. ,As is well known, :every aircraft has electrical power Vrequirements which are nor.-

mally *satisfied -by the inclusion 'of aV generator 'in nthe engine assembly at one .point or another. This generator normallyweighs 's'everal'pounds and is driven directly by the engine. Whileaircraft generators normally are relacordance with this invention that by concentrating the mass of an electric generator as far as possible near its radial eXtremity Vand by building a generator which is in y essence a flywheel, tthe mass of iron which is necessary Y6o y tively ismall-diafneter machines, Vit has been found in acy normally engaged, `andoperation fof clutch actuators y15 land 16 serve to disengage the clutches. `Switch 31 is 'therefore so 'connecteditovthrott-le 19' thatswitchl vremains open unless, the Ithrottle is advancedto at A-least Y one-third position, Le., to 1a positioncalling for roughly one-third of the mated power output of the engine. Assuming, therefore, thatftih'rottleV 19r is advanced to` normal cruising position, switch 3'1`is closed fand current flows through switch 3-1 to switch 27, thence toswitch 28 and to winding 30` `of clutch actuator y16. Now, asyhasvbeen .previously related, 'switches 2.7v and `28 are open during normal operation of the engine. However, should the engine malfunction and cease toy deliver driving torque, due to the load whicha deadengine places onthe system, the enginewhich remains in function-ingwconditionwill @drive the malfunctioning engine through fthe gearing and clutch system shown in FIG. `1. If the malfunctioning engine is now being driven rather than driving, the-direction of reaction torque applied l to the airframe 9 is reversed with Ithe result thatsprings 25 and 26 Aare corn-y pressed and springs 23 and 24are extended. This causes switches 27 and 28 to close, permitting current to flow to clutch actuator Winding 30, resulting in actuation of the clutch and disengagement of the malfunctioning engine from the gear box 6.

To prevent energization of clutch actuator y16due to momentary faltering of the engine orrnomentary torque reversals for other cau-ses, a time delay circuit` comprising resistor 32 and capacitor 33 is provided. The effect of this network is that if switches 27 and 28 are suddenly closed, a predetermined time will el-apse while capacitor l 33 is being charged before winding 30 is actually energized. If during this period switches 27 and 28 are again opened, Winding 30 will not be energized and clutch actuator 16 will not function; Resistor 32, which should be of relatively high resistance, is provided for slowly discharging capacitor 33 so that both its plates are normally |at `ground potential. The time delay afforded by the network comprised of resistor 3-2. and capacitor 33 should normally be of the order of three or four seconds in order that disengagement of the clutches does not occur for momentary power fluctuations such as might be caused by one of the engines 'cylinders missing or back-firing.

Switch 34, which connects battery 29 directly to wind- `ing 30, is provided for test purposes so that for ground check-out the engines may be run up independently as desired.

Referring now to FIG. 5, a detailed sectional vieW of the combination clutch, flywheel and alternator of this invention is shown. Casing 35 is bolted directly to engine 1 and carries stator 36, made up of laminated iron and a series field winding, at its periphery. Also carried by casing 35 are brushes 37 yand 38 which engage slip rings 39 and 40 on rotor 41 of the alternator portion of the invention. lIt will be noted from lFIG. 5 that rotor 41 is of unconventional design in that, among other things, the mass of the rotor is concentrated very largely at the periphery. The rotor is made up of interlocking, opposed, pointed pole pieces 42. which surround winding 43, 'which is connected at either end to slip rings 3-9 and 40. Pole pieces 43 are held in place by rotor frame members 44 and 45, which are essentially flat, annular plates at their extremity and which also carry clutch bands 46 and `47 of friction material, as shown. Rotor iframe member 44 is lsecured to the shaft of the engine by means of raised bosses 48 and 48a which receive bolts from the standard flange of the engine shaft. Thus, it is apparent that rotor 41 rotates 'continuously whenever the engine is rotating. Clutch discs 49 and 50 .are keyed to output shaft 51, which in turn is attached to the gear box, as shown in FIG. 2. Clutch Idiscs 49 and 50 are free to slide on shaft 511 and are normally held apart by compression springs 52 which `are provided .around the periphery of the clutch plates. When these clutch plates are held apart, they engage friction material 46 and cause engagement of the clutch. It will 'be noted that rotor frame member 45 is open in its central portion and that bearings 53, 54 and 55 permit clutch engagement collars 56, 57 and 58 to rotate freely with respect .to the shaft. Shaft S1 has attached to it end thrust :collar 59l which, in turn, keeps collars 56, 57 and 58 from translating to the left on the shaft.

It will be noted that yclutch engagement lcollars 56, 57 and 58 are, in reality, truncated, hollow cylinders, i.e., the central collar 57 is wedge-shaped when viewed in elevation, so that when it is rotated 'out of the position shown .in FIG. 5, collars 58 and 5,6 separate. Since rcollar 59 prevents translation of collar 58 to the left in FIG. 5, the result of rotating collar 57 is -a translation of coll-ar 56 to the right. 'Hou/ever, since springs 52 are provided,

shaft 51 moves to the left to the same extent as collar -56 moves to the right. In other Words, rotation of collar 57 causes plates 49 and 50'to approach each other and become disengaged from friction material 46.

Collar 57 is caused to rotate by lgear 60, which is chaindriven from gear 61` on actuator 15, which in turn is 6 caused to operate by current flowing -frorn switch 14 in FIG. 1. l

Thus, it can be seen from FIGS.v 5 and 7 that when the clutch is engaged the entire rotor forthe device shown in `lflIG. 5 serves as a flywheel. Both parts of the clutch rotate as well as the rotor of the alternator. 'Ihe entire moment of inertia of the rotor is thus available for flywheel purposes.

Since the rnass thereof is concentrated at the periphery of the rotor, its effectiveness as a flywheel is relatively lar-ge in comparison to its. actual mass.

Electrically, the alternator functions by having direct current from the aircraft electrical system applied to stator 36 in a conventional manner to create a magnetic field. Output alternating current is derived from Winding 42 through slip rings 39 and 40 and brushes 37 and 38. 'I'his alternating current may be rectified in a conventional manner and fed back to the electrical system of the aircraft to replenish its batteries. The function of springs S2 is to assure that clutch discs 49 and 50 lapply an even pressure to friction material 46 throughout the circumference of the clutch. Also, by the use of multiple springs at the periphery of the clutch, it canl be seen that the flywheel effect of the tota-l assembly is considerably enhanced.

While in the preferred embodiment of the invention a combination flywheel, alternator and clutch has been disclosed, it should be noted that the paramount advantage of the invention, -i.e., the ability to disconnect a disabled power plant and still continue flying, can be achieved 'as shown in the block diagram of FIG. l Without consolidating the design of the flywheel, clutch and alternator. The modification shown in FIGS. 5 and 7 does, however, effect a substantial saving in weight, and makes the use of this disconnect system feasible under certain conditions whereV it would otherwise not be feasible from the weight standpoint.

Although the present invention h-as been described with a 'certain degree of particularity, it is understood that various modifications in .the details and arrangements of parts may be had With-out departing from the spirit and scope of the invention las hereinafter claimed.

I claim:

l. A combination clutch, flywheel :and electric generator rotor comprising a pair of coaxially arranged spaced apart driving discs, ferromagnetic material joining said discs around the periphery thereof wherein the mass of said rotor is substantially concentrated, yfriction material on the inside facing surfaces of said discs, an output shaft coaxial with said discs, a pair of rcoaXially arranged driven discs keyed to said shaft between said driving discs `and movable into contact with said driving disc friction material, and a plurality of equally spaced compression springs separating said driven discs and normally urging them apart and into engagement with said driving discs.

2. A device as recited in claim 1 and further .comprising actuator means on said shaft for Idrawing said driven discs together and out of engagement with said driving discs, said actuator means comprising truncated hollow cylindrical members slidably mounted on said driven shaft and having their adjoining surfaces defined by planes which :are displaced by `an acute angle from -a plane which is normal to the axis of said driven shaft such that rotative displacement of one of -said cylindrical members relative to the other of said cylindrical members Icompresses said springs and causes said clutch plates to be Y 7 i Y brlish means contaoting said slip rings to thereby provide a eombination clutch flywheel and electrie generator.l

' -4L -A ,feombinationywheeL clutch and generator v'struc-V turejeonip'ri-sing a drive shaft, a circular disc attached tov Y V,be driven by said drive shaft, `an lannular disc coaxial ,with said '.eirrcular disc and spaced apart therefrom, ferrot Y magnetic material joining said'discs around their periphery wherein the mass of 'said flywheel is substantially concentrated, frietion material 'on the facing `surfaces of said difscs, a pair 'of annular oltehrplates'be'tween 'said disesk yand coaxial therewith, a driven shaft, meansv driv- Vin'gly conneeting said clutch plates `to said driven shaft While ,permitting translational .freedom therebetween, land la `@plural-ity `of y 'uniformly `spaced CompressionY springs Y separating said clutch plates at their periphery and lfore- Y planes which .are displaced by -an acute angle from fa plane which vis normal to fthe` axis of said driven shaft such that rotativedisplacement,of one of said cylindrical t Y members relative to the other of said cylindricallmembers compresses said spa-ings and causes said eluftchplates to be draw-n together.

6'. Adeviee as recited in claim '5, and further comprising la ygenerator stator situated radially outboard from and Y in magnetic cooperation with sai-d ferromagnetic material, electromagnetic windings in said ferromagnetic material arnanged to eut magneti-c lines |of flux between 'said ferro,-

Vmagnetic material and said stator, slip rings on one of said driving discs connected to said windings and brush means contacting said slip :rings to thereby provide-1a combination lelutch flywheel and electric:V generator.

References Cited in the le of this patent i UNITED STATES PATENTS 1,703,788 Skinner -i Peb. 2,6, k1929V 1,946,513 Webster et al. Feb. 13, 19'34 i v FOREIGN PATENTS 152,037 Germany June 16, 1904 

1. A COMBINATION CLUTCH, FLYWHEEL AND ELECTRIC GENERATOR ROTOR COMPRISING A PAIR OF COAXIALLY ARRANGED SPACED APART DRIVING DISCS, FERROMAGNETIC MATERIAL JOINING SAID DISCS AROUND THE PERIPHERY THEREOF WHEREIN THE MASS OF SAID ROTOR IS SUBSTANTIALLY CONCENTRATED, FRICTION MATERIAL ON THE INSIDE FACING SURFACES OF SAID DISCS, AN OUTPUT SHAFT COAXIAL WITH SAID DISCS, A PAIR OF COAXIALLY ARRANGED DRIVEN DISCS KEYED TO SAID SHAFT BETWEEN SAID DRIVING DISCS AND MOVABLE INTO CONTACT WITH SAID DRIVING DISC FRICTION MATERIAL, AND A PLURALITY OF EQUALLY SPACED COMPRESSION SPRINGS SEPARATING SAID DRIVEN DISCS AND NORMALLY URGING THEM APART AND INTO ENGAGEMENT WITH SAID DRIVING DISCS. 